The International Commission on Radiation Units and Measurements (ICRU), has as its principal objective the development of internationally acceptable recommendations regarding: (1) Quantities and units of radiation and radioactivity, (2) Procedures suitable for the measurement and application of these quantities in clinical radiology and radiobiology, (3) Physical data needed in the application of these procedures, the use of which tend to assure uniformity in reporting. The Commission also considers and makes similar types of recommendations on quantities, units and measurement techniques for the radiation protection field. The ICRU endeavors to collect and evaluate the latest data and information pertinent to the problems of radiation measurement and dosimetry and to recommend the most acceptable values for current use. The Commission's recommendations are kept under continual review in order to keep abreast of the rapidly expanding uses of radiation. After identification of an area in which ICRU recommendations would be useful, the Commission initiates research aimed at: (1) assessment of the available information which is pertinent to the problem, (2) identification of areas where more information is needed; (3) synthesis of present knowledge relevant to the problem area into practical recommendations on radiation quantities, units and measurement technology, which also highlight areas in need of further study. The Commission's program is a broad one and is continually changing to meet newly identified needs. However, the Commission's work is illustrated by the following list of representative projects on which research is underway: methods of assessment of dose in tracer investigations, modulation transfer function--its definition and measurement, neutron dosimetry in biology and medicine and dosimetry in radiobiology.